KeyMapper.txt

document.addEventListener("keydown", function (event) {
if (event.which == 72) {
triggerKeyboardEvent(document, 65);
} else if (event.which == 75) {
triggerKeyboardEvent(document, 68);
}
});


function triggerKeyboardEvent(el, keyCode){
    var keyboardEvent = document.createEvent("KeyboardEvent");
    
    var initMethod = typeof keyboardEvent.initKeyboardEvent !== 'undefined' ? "initKeyboardEvent" : "initKeyEvent";
  
  
    keyboardEvent[initMethod](
                       "keydown",
                        true,      // bubbles oOooOOo0
                        true,      // cancelable   
                        window,    // view
                        false,     // ctrlKeyArg
                        false,     // altKeyArg
                        false,     // shiftKeyArg
                        false,     // metaKeyArg
                        keyCode,  
                        0          // charCode   
    );
  
    el.dispatchEvent(keyboardEvent); 
}

http://jsbin.com/nalefohu/1/edit

function __triggerKeyboardEvent(el, keyCode)
{
    var eventObj = document.createEventObject ?
        document.createEventObject() : document.createEvent("Events");
  
    if(eventObj.initEvent){
      eventObj.initEvent("keydown", true, true);
    }
  
    eventObj.keyCode = keyCode;
    eventObj.which = keyCode;
    
    el.dispatchEvent ? el.dispatchEvent(eventObj) : el.fireEvent("onkeydown", eventObj); 
  
}

http://rudradevbasak.github.io/16384_hex/

http://www.lsauer.com/2011/08/javascript-keymap-keycodes-in-json.html

http://jsfiddle.net/npF3d/4/

https://mxr.mozilla.org/mozilla-central/source/dom/interfaces/events/nsIDOMKeyEvent.idl